Electrical fuse.



1. H. NAYLOR.

ELECTRICAL FUSE.

APPLICATLON FILED NOV. 17, 1913.

1 ,257, 1 O0. Petenfed Feb. 19, 1918.

.TGHN lbAYl-ZGE, @E MASSA@ ELECTRGLL Specification .Letters iatented 13.9, 191%.

pplieaton filed November 1?, T513.. Serial Re. 8GL398. l

To all wim/u, may; concern.'

lie it known that. L HN Namen, n citizen ofthe United States, residing at llverett, lr the county of Middlesex and State oi Mar i chusetts, have invented new and useful improvements in. Elec*- cal Fuses, of which the following is a speci tion.

This invention relates to improvements in electrical fuses. More particularly it relates to fuses of the cartridge type, in which a fusible conductor is inclosed withina non-conducting protective casing, which may be of liber and provided externally with metallic tips through which the internal conductor is connected. The casing serves to protect the fusible conductor, to protect the surroundings when the fuse blows` and to hold a filling of plaster, chalk, or other granular material which extinguishes the arc that may forni, protects the casing and absorbs the excess of gases of fusion or combustion. An attendant usually cannot tell by its external appearance whether a fuse of that general type is in working condition or not; so that when there is trouble in an electric installation presumably due to the blowing of some fuse therein, the attendant has to examine a number' of fuses, the examination in each case requiring not a little time in order to determine which particular fuse is the one that has blown. And when the proper fuse has been located an inordinate amount of time is further required to replace the fused conductor with a whole one. The objects of the present invention are to save the time of the attendantin locating the trouble and also to save his time in correcting it when located, as well as provide the other advantages which are characteristic of or incidental to the construction hereinafter set forth. These objects are attained by providing means for rapidly inspecting the interior of the normally closed casing; and by providing direct and instantaneously ef fected compressive connections between the internal fusible material and the external terminals of the fuse. The former is pref erably accomplished by providing a doublebarreled casing, one barrel surrounding the other and being movable thereon, and each having an opening adapted to register with an opening in the other; and the latter is preferably accomplished by providing a knife blade detachable terminal in the roi-.ei et wedge which makes direct, lateral.

temporarily heid, in position for fastening by having one end straight and the other bent at right angles. Variations may, however, be made from the preferred construe tion indicated, without departing from the scope of the invention as pointed out in the appended claims, the purpose of which is to. cover whatever features of novelty exist in the construction disclosed.

In the accompanying drawings Figure 1 is a side view of an embodiment of the invention;

Fig. 2 is an end View in section on the line 2*@ of Fig. l;

Figs. 3 and t are sectional views. on medial planes cutting the casing at right angles to each other, but leaving the terminals and fusible part;

Fig. 5 is an end view;

Figs. G and 7 are sectional views of a modified form, cutting ,the casing on medial planes at right angles to eachother, but leaving the terminals and fusible portion;

Fig. 8 is an end view of the same; and

Fig. 9 is a side view of another modification.

Referring to the drawings, 10 indicates a fusible conductor, which may be of any suitable style, the form represented in Fig. 1 being a ribbon or fiat strip. In the complete fuse this is inclosed in a stiff insulating cylinder 11, preferably of fiber board, and is surrounded therein by granular gas-absorb ing, arc-breal ing material such as chalk 19.. Vent. holes 13 may be provided if desired. The fusible member is connected with the outside circuit through metallic terminals. The knife blade arrangement consisting of flat blades projecting in the longitudinal direction of the fuse is illustrated in Figs. 1-G where the knife blades, markedili, pass movably through slots 15 in end caps 16, and through slots or holes 18 in the fiber plugs 17 which close the ends of the fiber cylinder 11. These two openings, 15 1S, are of suitable size to receive the inward projecting end of the external terminal and the outward projecting end of the internal fusible conductor. The slot 1S is Haring, on the inside, as at 18. The inner portion of the knife blade terminal is formed in the shape of a wedge; its outer portion is of any desired or suitable shape. One end of the fusible ribbon is straight; the other end is bent at right angles, forming a little hook 10. These parts are assembled by holding the cylinder 11 in hand, dropping the fusible strip 10 endwise into it, through the openings 15, 18, in one end and the openings 18, 15 in the further end until it rests upon the hook end 10; and then simply driving the knife blade terminals inward. Their wedging action makes good mechanical and electrical connections between them and the strip. The barrel 11 may then be iilled with chalk 12 through the lateral opening 20 and closed by rotating the external barrel 21 upon the inner barrel. The opening 20 through the barrel 11 and the opening 22 through the barrel 21 need be only large enough to permit easy inspection of the 1nterior, or to permit of shaking out the chalk or of introducing chalk when a fusible strip is renewed. It is not required to be large enough to admit the whole fuse and tools for putting it in place, norwould that be of advantage, because the fusible strip in the form illustrated is introduced and fastened practically instantaneously by the described action through the ends. The remains of a fused strip may be removed by pulling out the knife blade terminals endwise, when the fragments of the strip will readily fall out. The vent holes 13 may be omitted if desired and reliance placed on the cracks at the edges 0f the holes 16, 18, where the knife blade enters. The double construction of barrel possesses several advantages, one of which iS that it permits'the use of relatively thin stock. The places Where the stock is sin le when the fuse is closed, owing to its un erlying the opening in the other barrel, are not especially elements of weakness because the structure of the single barrel at those places is in arch form and is closely supported on either side. The outer barrel is conveniently held in place by expanding the terminal caps 16 at their inner ends as at 23, these caps being themselves held in place by screws 24 which may pass through the inner barrel and into its terminal plugs. The flaring shape 18 makes the fusible strip 10 self centering when inserted.

For the purposes of the invention the knife blade terminals may be completely removable as represented in Figs. 6-8, but preferably they, as in Fig. 3, are provided with an arrangement which preserves fully the wedge fastening and the instantaneous insertibility and removability of the fusible strip as described above, while not permitting the actual removal of the knife blade terminals during ordinary manipulation. In this case the wedge-shaped portion of the knife blade is somewhat larger than the slot 15, there being a shoulder 15', which engages the inside of the cap 16 when the knife fuse strip may be employed without the double incasing barrel; and the opening in the barrel 11 may be opened or closed by other means than that illustrated in Fig. 1, or in some cases that opening may be omitted all together. For example, in Figs. 6-8 is shown a single cylindrical casing 11, closed with a fiber plug and an entirely removable knife blade 14 at each end. This fuse may be used by inserting the fusible strip and the knife blade 14 at one end, then filling the interior with chalk through the slot 18 remaining at the other end, and afterward closing that opening by putting in the other knife blade. The condition of this fuse can be quickly examined by slipping it out of its place in the circuit, removing the knife blade at either end and' trying to pull out the fuse. If the strip has been fused one of the remaining ends will come away easily, otherwise not. With such a fuse the terminal caps 16 may be omitted if thought advisable.

Although the construction described is directly suitable for knife blade terminals, it is also applicable to plug fuses, one form of adaptability to that type being illustrated in Fig. 1 where the outer projecting end of the knife blade may be imagined as cut off rather short, only long enough in fact to serve as a handle or lug for easy loosening of the wedge. The cap 16 is provided with a spring lip 14 adapted to press against the knife blade when the latter is inserted. When a plug fuse is to be constructed, therefore, the cap 16 serves as the terminal and the current goes through this spring to the projecting end of the wedge. This spring may be formed integral with the cap and may in fact constitute the metal which is cut out and bent away is order to make the slot 15, as illustrated in Fig. 4. If the knife blades be left as long as illustrated the fuse may be used as either a plug fuse or knife blade fuse.

Another method of employing the invention is illustrated in Fig. 9 where there are two cylindrical casings, the outer one'2l' being intact and removable endwise, slipping out over the knife blades, and the inner having a lateral hole. To examine the condition of this fuse one slips the outer casing longitudinally far enough to look through the hole into the internal cylinder.

While a metallic strip of ribbon form is illustrated for the fusible element it will be obvious that the term strip may include 'puts it into the casing.

I claim as my invention 1. A safety fuse comprisin s a fusible member, a cylindrical casing t erefor and caps covering the ends thereof, said caps having out-turned flanges at their inner ends and another cylindrical easing mounted rotatably on the first and held in position by said cap flanges, each casin having an opening adapted to be brought into register with the opening in the other upon rotation of the said outer casing.

2. A safety fuse comprising a fusible member with casing therefor, plugs in the ends of the casing having openings through which the fusible member passes and external terminals for the fuse having inner ends comprisin wedges and means preventing the removoof said terminals while permitting the removal of said wedges from their seats, thereby permitting insertion and removal of the fusible member through said openings. f

3. A safety fuse comprising a fusible member with casing therefor, plugs in the ends of the casin having openings through which the fusib e member passes and external terminals for the fuse having inner ends comprising wedges adapted to be driven into said o enings for holding and connecting the fusible member, caps inclosing the ends of the casing, through which the wedge members pass, and springs thereon adapted to bear upon said wedge members when inserted therein, making electrical connection with said caps.

4. A safety fuse comprising a fusible member and a casing therefor having terminal openings through which the fusible member extends to the exterior, said fusible member being formed at one end to slip loosely through both of said openings and at the other end to support itself by engaging an exterior part and hanging thereon; exteriory terminals for electrical connection, extending into said openings; and means whereby their insertion makes fast the terminal and fusible member in electrical connection.

Signed by me at Boston, Mass., this fifteenth day of October, 1913.

JOHN H. NAYLOR.

Witnesses:`

Evnnm'r E. KENT, ANNA B. LINDSAY. 

